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# Pre calc help exact value, quadrant II?

How do you solve this??

Find the exact value of the expression given that sec x= -13/12 and

csec y= 5/4, x and y are in quadrant II

1) cos 2x

2) sin 2x

3) tan (x+ y)

### 1 Answer

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- DWReadLv 77 years ago
sec(x) = -13/12

cos(x) = -12/13

sin²(x) = 1 - cos²(x) = 25/169

sin(x) = √(25/169) = 5/13

Use double-angle formulas

cos(2x) = 1 - 2sin²(x)

sin(2x) = 2sin(x)cos(x)

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